It has been recently known that in view of reduction in rolling resistance and improvement of low fuel consumption, a silica powder, as a filler, is contained in a vehicle tire or the like.
Such a silica powder is usually blended in a rubber composition that is a material of the vehicle tire or the like. However, there is a disadvantage that the silica powder easily scatters, so that the usability thereof at the time of mixing is poor, and the non-uniform scattering amount causes unevenness in the mixing amount, so that the quality of products is non-uniform.
Thus, it has been considered that silica is used by being agglomerated so as to prevent the scattering of the silica. To be specific, as a method for agglomerating the silica, for example, a method in which water, an organic solvent, or a mixture thereof are added to powdered silica to be stirred and agglomerated has been proposed (ref: Patent Document 1).